The present invention relates generally to methods and apparatuses for manufacturing Cathode Ray Tubes (CRTs), and more particularly to methods and apparatuses for manufacturing CRTs in which a vacuum is maintained on multiple CRT""s during the manufacturing process.
During the manufacture of CRT""s, such as small profile 7 inch CRT""s for example, part of the manufacturing process includes drawing a vacuum on every CRT, while baking the CRT""s in an exhaust oven. This is typically performed utilizing exhaust carts, which permit drawing a vacuum on four CRT""s simultaneously. Each exhaust cart comprises a manifold with ports connected to each CRT. A vacuum is drawn on the entire manifold and thereby on the 4 CRT""s under preparation.
A drawback of this approach, however, is that in the event that one CRT breaks, the vacuum is destroyed for all the CRT""s under manufacture, thereby rendering all the CRT""s being prepared ultimately defective since baking then occurs in the absence of a vacuum.
The present invention is therefore directed to the problem for developing a method and apparatus for isolating a damaged or broken CRT connected to an exhaust cart during the vacuum extraction process, thereby preserving the vacuum in the unbroken CRT""s under fabrication and thus preventing collateral damage to otherwise undamaged units connected to the exhaust cart during the baking process.
The present invention solves this problem by providing a valve assembly installed in an exhaust cart manifold port that effectively seals off the manifold port connected to a CRT in which a vacuum is compromised due to structural failure. By sealing off the port connected to the defective CRT under preparation, the vacuum to the other CRT""s under preparation is not be compromised and production defects to these CRT""s as a result of a single defective CRT can be avoided.
According to one aspect of the present invention, a device for controlling the flow through a vacuum extraction manifold port includes a hollow pipe having a first portion and a second portion and a cavity that includes a retaining surface disposed within it. The pipe also includes exit ports and a poppet having a front section and a rear section mounted so as to be able to slide within the pipe cavity. The front section of the poppet is attached to the first portion of the pipe by a biasing means. The device also includes an actuator rod disposed within the cavity. The actuator rod has a first end attached to the rear section of said poppet, and a second end connected to actuating means disposed at the second portion of the pipe.
During introduction of a gaseous flow into the first portion of the pipe at less than a first pressure value, the poppet remains in an intermediate position in the pipe cavity thereby permitting the gaseous flow to travel through the first portion of the pipe, past the poppet and through the exit ports, thereby exiting the pipe.
During introduction of the gaseous flow into the first portion of the pipe at greater than a second pressure value, however, the pressure of the gaseous flow causes the poppet to slide against the retaining surface thereby establishing a seal confining the gaseous flow within said cavity and eliminating further flow through the pipe.
During introduction of the gaseous flow at greater than a third pressure value, the actuating means causes the actuator rod to drive the poppet against the retaining ring thereby establishing the seal and confining said gaseous flow within the pipe cavity and eliminating further flow through the pipe.
According to another aspect of the present invention, in the above device the pipe is fabricated of steel.
According to another aspect of the present invention, in the above device, the exit ports are perforations in the pipe.
According to yet another aspect of the present invention, in the above device, the biasing means includes at least one spring.
According to another aspect of the present invention, in the above device, the actuating means includes a linear actuator.
According to another aspect of the present invention, in the above device, the linear actuator includes pressure-sensing means.
According to another aspect of the present invention, in the above device, the gaseous flow includes air contained in a CRT connected to the pipe.
According to another aspect of the invention, in the above device, the pipe has an annular shape.
According to another aspect of the present invention, in the above device, the intermediate position occupied by the poppet is a position between the biasing means and the retaining surface.
According to another aspect of the invention, in the above device, the gaseous flow is generated by a vacuum pump extracting a gas from a vessel attached to said first portion of said pipe.
According to another aspect of the invention, a device for controlling gaseous flow in a vacuum extraction manifold port includes a hollow pipe having a first portion and a second portion. The pipe includes a cavity with a retaining surface. The pipe also includes a poppet mounted within the pipe cavity such that it is able to slide within the cavity. The poppet has a front section and a rear section and is connected to the first portion of the pipe by a first biasing means attached to the front section of the poppet. The poppet is also connected to the second portion of the pipe by a second biasing means attached to the rear section of the poppet. Also contained in the pipe are exit vents to permit the escape of a gaseous flow through the pipe.
During introduction of the gaseous flow into the first portion of the pipe at less than a first pressure value, the poppet remains in an intermediate position within the cavity thereby permitting the gaseous flow to travel through the first portion of the pipe, past the poppet and exit the pipe through the exit ports.
During introduction of the gaseous flow into the first portion of the pipe at greater than a second pressure value, the pressure of the gaseous flow causes the poppet to slide against the retaining surface thereby establishing a seal confining the gaseous flow within the cavity and preventing further gaseous flow to exit the pipe.
During introduction of the gaseous flow at greater than a third pressure value the second biasing means forces the poppet against the retaining surface thereby establishing the seal confining the gaseous flow within the cavity and preventing further flow through the pipe.
According to another aspect of the present invention, in the above device, the pipe is fabricated of steel.
According to another aspect of the present invention, in the above device, the exit ports include perforations in the pipe.
According to another aspect of the present invention, in the above device, the first biasing means includes at least one spring.
According to yet another aspect of the present invention, in the above device, the second biasing means includes a linear actuator and actuating rod.
According to another aspect of the present invention, in the above device, the linear actuator includes pressure-sensing means.
According to another aspect of the invention, in the above device, the gaseous flow includes air contained in a Cathode Ray Tube connected to the pipe.
According to another aspect of the invention, in the above device, the pipe is annular in shape.
According to yet another aspect of the present invention, in the above device, the intermediate position is a position between the first biasing means and the retaining surface.
According to yet another aspect of the present invention, in the above device, the gaseous flow is generated by a vacuum pump extracting a gas from a vessel connected to the first portion of the pipe.
According to another aspect of the present invention, a method of controlling the flow in a vacuum extraction manifold port includes (1.) introducing a gaseous flow into a hollow pipe having valving means to confine the gaseous flow within the pipe. The valving means is operatively connected to first and second biasing means and is operated by either of the first and second biasing means, (2.) detecting the pressure of the gaseous flow; and permitting said gaseous flow to exit the pipe when the pressure is less than a first value, (3.) actuating the valving means via the first biasing means when the pressure exceeds a second value, and (4.) actuating the valving means via the second biasing means when the pressure exceeds a third value.
According to another aspect of the present invention, in the above method, the pipe is fabricated of steel.
According to another aspect of the present invention, in the above method, the valving means comprises a sliding poppet disposed within a cavity in said pipe operating in conjunction with a retaining surface.
According to another aspect of the present invention, in the above method, the first biasing means includes at least one spring.
According to another aspect of the present invention, in the above method, the second biasing means comprises a pressure sensitive linear actuator and actuator rod.